Update documentation

adapter/experimental.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"net"
 
+	"github.com/sagernet/sing-box/common/urltest"
 	N "github.com/sagernet/sing/common/network"
 )
 
@@ -12,6 +13,7 @@ type ClashServer interface {
 	Mode() string
 	StoreSelected() bool
 	CacheFile() ClashCacheFile
+	HistoryStorage() *urltest.HistoryStorage
 	RoutedConnection(ctx context.Context, conn net.Conn, metadata InboundContext, matchedRule Rule) (net.Conn, Tracker)
 	RoutedPacketConnection(ctx context.Context, conn N.PacketConn, metadata InboundContext, matchedRule Rule) (N.PacketConn, Tracker)
 }

common/baderror/baderror.go

@@ -26,7 +26,7 @@ func WrapH2(err error) error {
 	if err == io.ErrUnexpectedEOF {
 		return io.EOF
 	}
-	if Contains(err, "client disconnected", "body closed by handler") {
+	if Contains(err, "client disconnected", "body closed by handler", "response body closed", "; CANCEL") {
 		return net.ErrClosed
 	}
 	return err

constant/proxy.go

@@ -25,4 +25,5 @@ const (
 
 const (
 	TypeSelector = "selector"
+	TypeURLTest  = "urltest"
 )

constant/timeout.go

@@ -3,10 +3,11 @@ package constant
 import "time"
 
 const (
-	TCPTimeout         = 5 * time.Second
-	ReadPayloadTimeout = 300 * time.Millisecond
-	DNSTimeout         = 10 * time.Second
-	QUICTimeout        = 30 * time.Second
-	STUNTimeout        = 15 * time.Second
-	UDPTimeout         = 5 * time.Minute
+	TCPTimeout             = 5 * time.Second
+	ReadPayloadTimeout     = 300 * time.Millisecond
+	DNSTimeout             = 10 * time.Second
+	QUICTimeout            = 30 * time.Second
+	STUNTimeout            = 15 * time.Second
+	UDPTimeout             = 5 * time.Minute
+	DefaultURLTestInterval = 1 * time.Minute
 )

constant/version.go

@@ -1,3 +1,3 @@
 package constant
 
-var Version = "1.1-beta5"
+var Version = "1.1-beta6"

docs/changelog.md

@@ -1,3 +1,8 @@
+#### 1.1-beta6
+
+* Add [URLTest outbound](/configuration/outbound/urltest)
+* Fix bugs in 1.1-beta5
+
 #### 1.1-beta5
 
 * Print tags in version command

docs/configuration/outbound/index.md

@@ -15,21 +15,24 @@
 
 ### Fields
 
-| Type          | Format                       |
-|---------------|------------------------------|
-| `direct`      | [Direct](./direct)           |
-| `block`       | [Block](./block)             |
-| `socks`       | [SOCKS](./socks)             |
-| `http`        | [HTTP](./http)               |
-| `shadowsocks` | [Shadowsocks](./shadowsocks) |
-| `vmess`       | [VMess](./vmess)             |
-| `trojan`      | [Trojan](./trojan)           |
-| `wireguard`   | [Wireguard](./wireguard)     |
-| `hysteria`    | [Hysteria](./hysteria)       |
-| `tor`         | [Tor](./tor)                 |
-| `ssh`         | [SSH](./ssh)                 |
-| `dns`         | [DNS](./dns)                 |
-| `selector`    | [Selector](./selector)       |
+| Type           | Format                         |
+|----------------|--------------------------------|
+| `direct`       | [Direct](./direct)             |
+| `block`        | [Block](./block)               |
+| `socks`        | [SOCKS](./socks)               |
+| `http`         | [HTTP](./http)                 |
+| `shadowsocks`  | [Shadowsocks](./shadowsocks)   |
+| `vmess`        | [VMess](./vmess)               |
+| `trojan`       | [Trojan](./trojan)             |
+| `wireguard`    | [Wireguard](./wireguard)       |
+| `hysteria`     | [Hysteria](./hysteria)         |
+| `shadowsocksr` | [ShadowsocksR](./shadowsocksr) |
+| `vless`        | [VLESS](./vless)               |
+| `tor`          | [Tor](./tor)                   |
+| `ssh`          | [SSH](./ssh)                   |
+| `dns`          | [DNS](./dns)                   |
+| `selector`     | [Selector](./selector)         |
+| `urltest`      | [URLTest](./urltest)           |
 
 #### tag
 

docs/configuration/outbound/index.zh.md

@@ -15,21 +15,24 @@
 
 ### 字段
 
-| 类型            | 格式                           |
-|---------------|------------------------------|
-| `direct`      | [Direct](./direct)           |
-| `block`       | [Block](./block)             |
-| `socks`       | [SOCKS](./socks)             |
-| `http`        | [HTTP](./http)               |
-| `shadowsocks` | [Shadowsocks](./shadowsocks) |
-| `vmess`       | [VMess](./vmess)             |
-| `trojan`      | [Trojan](./trojan)           |
-| `wireguard`   | [Wireguard](./wireguard)     |
-| `hysteria`    | [Hysteria](./hysteria)       |
-| `tor`         | [Tor](./tor)                 |
-| `ssh`         | [SSH](./ssh)                 |
-| `dns`         | [DNS](./dns)                 |
-| `selector`    | [Selector](./selector)       |
+| 类型             | 格式                             |
+|----------------|--------------------------------|
+| `direct`       | [Direct](./direct)             |
+| `block`        | [Block](./block)               |
+| `socks`        | [SOCKS](./socks)               |
+| `http`         | [HTTP](./http)                 |
+| `shadowsocks`  | [Shadowsocks](./shadowsocks)   |
+| `vmess`        | [VMess](./vmess)               |
+| `trojan`       | [Trojan](./trojan)             |
+| `wireguard`    | [Wireguard](./wireguard)       |
+| `hysteria`     | [Hysteria](./hysteria)         |
+| `shadowsocksr` | [ShadowsocksR](./shadowsocksr) |
+| `vless`        | [VLESS](./vless)               |
+| `tor`          | [Tor](./tor)                   |
+| `ssh`          | [SSH](./ssh)                   |
+| `dns`          | [DNS](./dns)                   |
+| `selector`     | [Selector](./selector)         |
+| `urltest`      | [URLTest](./urltest)           |
 
 #### tag
 

docs/configuration/outbound/urltest.md

@@ -0,0 +1,37 @@
+### Structure
+
+```json
+{
+  "type": "urltest",
+  "tag": "auto",
+  
+  "outbounds": [
+    "proxy-a",
+    "proxy-b",
+    "proxy-c"
+  ],
+  "url": "http://www.gstatic.com/generate_204",
+  "interval": "1m",
+  "tolerance": 50
+}
+```
+
+### Fields
+
+#### outbounds
+
+==Required==
+
+List of outbound tags to test.
+
+#### url
+
+The URL to test. `http://www.gstatic.com/generate_204` will be used if empty.
+
+#### interval
+
+The test interval. `1m` will be used if empty.
+
+#### tolerance
+
+The test tolerance in milliseconds. `50` will be used if empty.

docs/configuration/outbound/urltest.zh.md

@@ -0,0 +1,37 @@
+### 结构
+
+```json
+{
+  "type": "urltest",
+  "tag": "auto",
+  
+  "outbounds": [
+    "proxy-a",
+    "proxy-b",
+    "proxy-c"
+  ],
+  "url": "http://www.gstatic.com/generate_204",
+  "interval": "1m",
+  "tolerance": 50
+}
+```
+
+### 字段
+
+#### outbounds
+
+==必填==
+
+用于测试的出站标签列表。
+
+#### url
+
+用于测试的链接。默认使用 `http://www.gstatic.com/generate_204`。
+
+#### interval
+
+测试间隔。 默认使用 `1m`。
+
+#### tolerance
+
+以毫秒为单位的测试容差。 默认使用 `50`。

experimental/clashapi/proxies.go

@@ -61,7 +61,6 @@ func findProxyByName(router adapter.Router) func(next http.Handler) http.Handler
 func proxyInfo(server *Server, detour adapter.Outbound) *badjson.JSONObject {
 	var info badjson.JSONObject
 	var clashType string
-	var isGroup bool
 	switch detour.Type() {
 	case C.TypeDirect:
 		clashType = "Direct"
@@ -91,7 +90,8 @@ func proxyInfo(server *Server, detour adapter.Outbound) *badjson.JSONObject {
 		clashType = "SSH"
 	case C.TypeSelector:
 		clashType = "Selector"
-		isGroup = true
+	case C.TypeURLTest:
+		clashType = "URLTest"
 	default:
 		clashType = "Direct"
 	}
@@ -104,10 +104,9 @@ func proxyInfo(server *Server, detour adapter.Outbound) *badjson.JSONObject {
 	} else {
 		info.Put("history", []*urltest.History{})
 	}
-	if isGroup {
-		selector := detour.(adapter.OutboundGroup)
-		info.Put("now", selector.Now())
-		info.Put("all", selector.All())
+	if group, isGroup := detour.(adapter.OutboundGroup); isGroup {
+		info.Put("now", group.Now())
+		info.Put("all", group.All())
 	}
 	return &info
 }

experimental/clashapi/server.go

@@ -144,6 +144,10 @@ func (s *Server) CacheFile() adapter.ClashCacheFile {
 	return s.cacheFile
 }
 
+func (s *Server) HistoryStorage() *urltest.HistoryStorage {
+	return s.urlTestHistory
+}
+
 func (s *Server) RoutedConnection(ctx context.Context, conn net.Conn, metadata adapter.InboundContext, matchedRule adapter.Rule) (net.Conn, adapter.Tracker) {
 	tracker := trafficontrol.NewTCPTracker(conn, s.trafficManager, castMetadata(metadata), s.router, matchedRule)
 	return tracker, tracker

go.mod

@@ -23,10 +23,10 @@ require (
 	github.com/pires/go-proxyproto v0.6.2
 	github.com/refraction-networking/utls v1.1.2
 	github.com/sagernet/quic-go v0.0.0-20220818150011-de611ab3e2bb
-	github.com/sagernet/sing v0.0.0-20220915031330-38f39bc0c690
-	github.com/sagernet/sing-dns v0.0.0-20220913115644-aebff1dfbba8
+	github.com/sagernet/sing v0.0.0-20220916071326-834794b006ea
+	github.com/sagernet/sing-dns v0.0.0-20220915084601-812e0864b45b
 	github.com/sagernet/sing-shadowsocks v0.0.0-20220819002358-7461bb09a8f6
-	github.com/sagernet/sing-tun v0.0.0-20220915032336-60b1da576469
+	github.com/sagernet/sing-tun v0.0.0-20220916073459-0032242c9617
 	github.com/sagernet/sing-vmess v0.0.0-20220913015714-c4ab86d40e12
 	github.com/sagernet/smux v0.0.0-20220831015742-e0f1988e3195
 	github.com/sagernet/websocket v0.0.0-20220913015213-615516348b4e

go.sum

@@ -145,14 +145,14 @@ github.com/sagernet/quic-go v0.0.0-20220818150011-de611ab3e2bb h1:wc0yQ+SBn4TaTY
 github.com/sagernet/quic-go v0.0.0-20220818150011-de611ab3e2bb/go.mod h1:MIccjRKnPTjWwAOpl+AUGWOkzyTd9tERytudxu+1ra4=
 github.com/sagernet/sing v0.0.0-20220812082120-05f9836bff8f/go.mod h1:QVsS5L/ZA2Q5UhQwLrn0Trw+msNd/NPGEhBKR/ioWiY=
 github.com/sagernet/sing v0.0.0-20220817130738-ce854cda8522/go.mod h1:QVsS5L/ZA2Q5UhQwLrn0Trw+msNd/NPGEhBKR/ioWiY=
-github.com/sagernet/sing v0.0.0-20220915031330-38f39bc0c690 h1:pvaLdkDmsGN2K46vf8rorAhYGFvKPuQNzcofuy3aXXg=
-github.com/sagernet/sing v0.0.0-20220915031330-38f39bc0c690/go.mod h1:x3NHUeJBQwV75L51zwmLKQdLtRvR+M4PmXkfQtU1vIY=
-github.com/sagernet/sing-dns v0.0.0-20220913115644-aebff1dfbba8 h1:Iyfl+Rm5jcDvXuy/jpOBI3eu35ujci50tkqYHHwwg+8=
-github.com/sagernet/sing-dns v0.0.0-20220913115644-aebff1dfbba8/go.mod h1:bPVnJ5gJ0WmUfN1bJP9Cis0ab8SSByx6JVzyLJjDMwA=
+github.com/sagernet/sing v0.0.0-20220916071326-834794b006ea h1:ZAWvZdeByPBBz3Vs+w3Erbh+DDo7D4biokoPhXl0nNU=
+github.com/sagernet/sing v0.0.0-20220916071326-834794b006ea/go.mod h1:x3NHUeJBQwV75L51zwmLKQdLtRvR+M4PmXkfQtU1vIY=
+github.com/sagernet/sing-dns v0.0.0-20220915084601-812e0864b45b h1:cXCMNJ9heZ+c6l+qUcku60x9KyXo4SOAaJfg/6spOmU=
+github.com/sagernet/sing-dns v0.0.0-20220915084601-812e0864b45b/go.mod h1:SrvWLfOSlnFmH32CWXicfilAGgIXR0VjrH6yRbuXYww=
 github.com/sagernet/sing-shadowsocks v0.0.0-20220819002358-7461bb09a8f6 h1:JJfDeYYhWunvtxsU/mOVNTmFQmnzGx9dY034qG6G3g4=
 github.com/sagernet/sing-shadowsocks v0.0.0-20220819002358-7461bb09a8f6/go.mod h1:EX3RbZvrwAkPI2nuGa78T2iQXmrkT+/VQtskjou42xM=
-github.com/sagernet/sing-tun v0.0.0-20220915032336-60b1da576469 h1:tvGUJsOqxZ3ofAY9undQfQ+JCWvmIwLpIOC+XaBFO88=
-github.com/sagernet/sing-tun v0.0.0-20220915032336-60b1da576469/go.mod h1:5AhPUv9jWDQ3pv3Mj78SL/1TSjhoaj6WNASxRKLqXqM=
+github.com/sagernet/sing-tun v0.0.0-20220916073459-0032242c9617 h1:fNTNmylhB/UjoBLusmrFu2B1fat4OCkDkQXTgrE7ZsE=
+github.com/sagernet/sing-tun v0.0.0-20220916073459-0032242c9617/go.mod h1:5AhPUv9jWDQ3pv3Mj78SL/1TSjhoaj6WNASxRKLqXqM=
 github.com/sagernet/sing-vmess v0.0.0-20220913015714-c4ab86d40e12 h1:4HYGbTDDemgBVTmaspXbkgjJlXc3hYVjNxSddJndq8Y=
 github.com/sagernet/sing-vmess v0.0.0-20220913015714-c4ab86d40e12/go.mod h1:u66Vv7NHXJWfeAmhh7JuJp/cwxmuQlM56QoZ7B7Mmd0=
 github.com/sagernet/smux v0.0.0-20220831015742-e0f1988e3195 h1:5VBIbVw9q7aKbrFdT83mjkyvQ+VaRsQ6yflTepfln38=

inbound/tun.go

@@ -190,7 +190,7 @@ func (t *Tun) NewConnection(ctx context.Context, conn net.Conn, upstreamMetadata
 	if err != nil {
 		t.NewError(ctx, err)
 	}
-	return err
+	return nil
 }
 
 func (t *Tun) NewPacketConnection(ctx context.Context, conn N.PacketConn, upstreamMetadata M.Metadata) error {
@@ -212,7 +212,7 @@ func (t *Tun) NewPacketConnection(ctx context.Context, conn N.PacketConn, upstre
 	if err != nil {
 		t.NewError(ctx, err)
 	}
-	return err
+	return nil
 }
 
 func (t *Tun) NewError(ctx context.Context, err error) {

mkdocs.yml

@@ -90,6 +90,7 @@ nav:
           - SSH: configuration/outbound/ssh.md
           - DNS: configuration/outbound/dns.md
           - Selector: configuration/outbound/selector.md
+          - URLTest: configuration/outbound/urltest.md
   - FAQ:
       - faq/index.md
       - Known Issues: faq/known-issues.md

option/clash.go

@@ -14,3 +14,10 @@ type SelectorOutboundOptions struct {
 	Outbounds []string `json:"outbounds"`
 	Default   string   `json:"default,omitempty"`
 }
+
+type URLTestOutboundOptions struct {
+	Outbounds []string `json:"outbounds"`
+	URL       string   `json:"url,omitempty"`
+	Interval  Duration `json:"interval,omitempty"`
+	Tolerance uint16   `json:"tolerance,omitempty"`
+}

option/outbound.go

@@ -24,6 +24,7 @@ type _Outbound struct {
 	ShadowsocksROptions ShadowsocksROutboundOptions `json:"-"`
 	VLESSOptions        VLESSOutboundOptions        `json:"-"`
 	SelectorOptions     SelectorOutboundOptions     `json:"-"`
+	URLTestOptions      URLTestOutboundOptions      `json:"-"`
 }
 
 type Outbound _Outbound
@@ -61,6 +62,8 @@ func (h Outbound) MarshalJSON() ([]byte, error) {
 		v = h.VLESSOptions
 	case C.TypeSelector:
 		v = h.SelectorOptions
+	case C.TypeURLTest:
+		v = h.URLTestOptions
 	default:
 		return nil, E.New("unknown outbound type: ", h.Type)
 	}
@@ -104,6 +107,8 @@ func (h *Outbound) UnmarshalJSON(bytes []byte) error {
 		v = &h.VLESSOptions
 	case C.TypeSelector:
 		v = &h.SelectorOptions
+	case C.TypeURLTest:
+		v = &h.URLTestOptions
 	default:
 		return E.New("unknown outbound type: ", h.Type)
 	}

outbound/builder.go

@@ -47,6 +47,8 @@ func New(ctx context.Context, router adapter.Router, logger log.ContextLogger, o
 		return NewVLESS(ctx, router, logger, options.Tag, options.VLESSOptions)
 	case C.TypeSelector:
 		return NewSelector(router, logger, options.Tag, options.SelectorOptions)
+	case C.TypeURLTest:
+		return NewURLTest(router, logger, options.Tag, options.URLTestOptions)
 	default:
 		return nil, E.New("unknown outbound type: ", options.Type)
 	}

outbound/urltest.go

@@ -0,0 +1,287 @@
+package outbound
+
+import (
+	"context"
+	"net"
+	"sort"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/urltest"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/batch"
+	E "github.com/sagernet/sing/common/exceptions"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+)
+
+var (
+	_ adapter.Outbound      = (*URLTest)(nil)
+	_ adapter.OutboundGroup = (*URLTest)(nil)
+)
+
+type URLTest struct {
+	myOutboundAdapter
+	tags      []string
+	link      string
+	interval  time.Duration
+	tolerance uint16
+	group     *URLTestGroup
+}
+
+func NewURLTest(router adapter.Router, logger log.ContextLogger, tag string, options option.URLTestOutboundOptions) (*URLTest, error) {
+	outbound := &URLTest{
+		myOutboundAdapter: myOutboundAdapter{
+			protocol: C.TypeURLTest,
+			router:   router,
+			logger:   logger,
+			tag:      tag,
+		},
+		tags:      options.Outbounds,
+		link:      options.URL,
+		interval:  time.Duration(options.Interval),
+		tolerance: options.Tolerance,
+	}
+	if len(outbound.tags) == 0 {
+		return nil, E.New("missing tags")
+	}
+	return outbound, nil
+}
+
+func (s *URLTest) Network() []string {
+	if s.group == nil {
+		return []string{N.NetworkTCP, N.NetworkUDP}
+	}
+	return s.group.Select(N.NetworkTCP).Network()
+}
+
+func (s *URLTest) Start() error {
+	outbounds := make([]adapter.Outbound, 0, len(s.tags))
+	for i, tag := range s.tags {
+		detour, loaded := s.router.Outbound(tag)
+		if !loaded {
+			return E.New("outbound ", i, " not found: ", tag)
+		}
+		outbounds = append(outbounds, detour)
+	}
+	s.group = NewURLTestGroup(s.router, s.logger, outbounds, s.link, s.interval, s.tolerance)
+	return s.group.Start()
+}
+
+func (s URLTest) Close() error {
+	return common.Close(
+		common.PtrOrNil(s.group),
+	)
+}
+
+func (s *URLTest) Now() string {
+	return s.group.Select(N.NetworkTCP).Tag()
+}
+
+func (s *URLTest) All() []string {
+	return s.tags
+}
+
+func (s *URLTest) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
+	outbound := s.group.Select(network)
+	conn, err := outbound.DialContext(ctx, network, destination)
+	if err == nil {
+		return conn, nil
+	}
+	s.logger.ErrorContext(ctx, err)
+	go s.group.checkOutbounds()
+	outbounds := s.group.Fallback(outbound)
+	for _, fallback := range outbounds {
+		conn, err = fallback.DialContext(ctx, network, destination)
+		if err == nil {
+			return conn, nil
+		}
+	}
+	return nil, err
+}
+
+func (s *URLTest) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {
+	outbound := s.group.Select(N.NetworkUDP)
+	conn, err := outbound.ListenPacket(ctx, destination)
+	if err == nil {
+		return conn, nil
+	}
+	s.logger.ErrorContext(ctx, err)
+	go s.group.checkOutbounds()
+	outbounds := s.group.Fallback(outbound)
+	for _, fallback := range outbounds {
+		conn, err = fallback.ListenPacket(ctx, destination)
+		if err == nil {
+			return conn, nil
+		}
+	}
+	return nil, err
+}
+
+func (s *URLTest) NewConnection(ctx context.Context, conn net.Conn, metadata adapter.InboundContext) error {
+	return NewConnection(ctx, s, conn, metadata)
+}
+
+func (s *URLTest) NewPacketConnection(ctx context.Context, conn N.PacketConn, metadata adapter.InboundContext) error {
+	return NewPacketConnection(ctx, s, conn, metadata)
+}
+
+type URLTestGroup struct {
+	router    adapter.Router
+	logger    log.Logger
+	outbounds []adapter.Outbound
+	link      string
+	interval  time.Duration
+	tolerance uint16
+	history   *urltest.HistoryStorage
+
+	ticker *time.Ticker
+	close  chan struct{}
+}
+
+func NewURLTestGroup(router adapter.Router, logger log.Logger, outbounds []adapter.Outbound, link string, interval time.Duration, tolerance uint16) *URLTestGroup {
+	if link == "" {
+		//goland:noinspection HttpUrlsUsage
+		link = "http://www.gstatic.com/generate_204"
+	}
+	if interval == 0 {
+		interval = C.TCPTimeout
+	}
+	if tolerance == 0 {
+		tolerance = 50
+	}
+	var history *urltest.HistoryStorage
+	if clashServer := router.ClashServer(); clashServer != nil {
+		history = clashServer.HistoryStorage()
+	} else {
+		history = urltest.NewHistoryStorage()
+	}
+	return &URLTestGroup{
+		router:    router,
+		logger:    logger,
+		outbounds: outbounds,
+		link:      link,
+		interval:  interval,
+		tolerance: tolerance,
+		history:   history,
+		close:     make(chan struct{}),
+	}
+}
+
+func (g *URLTestGroup) Start() error {
+	g.ticker = time.NewTicker(g.interval)
+	go g.loopCheck()
+	return nil
+}
+
+func (g *URLTestGroup) Close() error {
+	g.ticker.Stop()
+	close(g.close)
+	return nil
+}
+
+func (g *URLTestGroup) Select(network string) adapter.Outbound {
+	var minDelay uint16
+	var minTime time.Time
+	var minOutbound adapter.Outbound
+	for _, detour := range g.outbounds {
+		if !common.Contains(detour.Network(), network) {
+			continue
+		}
+		history := g.history.LoadURLTestHistory(RealTag(detour))
+		if history == nil {
+			continue
+		}
+		if minDelay == 0 || minDelay > history.Delay+g.tolerance || minDelay > history.Delay-g.tolerance && minTime.Before(history.Time) {
+			minDelay = history.Delay
+			minTime = history.Time
+			minOutbound = detour
+		}
+	}
+	if minOutbound == nil {
+		for _, detour := range g.outbounds {
+			if !common.Contains(detour.Network(), network) {
+				continue
+			}
+			minOutbound = detour
+			break
+		}
+	}
+	return minOutbound
+}
+
+func (g *URLTestGroup) Fallback(used adapter.Outbound) []adapter.Outbound {
+	outbounds := make([]adapter.Outbound, 0, len(g.outbounds)-1)
+	for _, detour := range g.outbounds {
+		if detour != used {
+			outbounds = append(outbounds, detour)
+		}
+	}
+	sort.Slice(outbounds, func(i, j int) bool {
+		oi := outbounds[i]
+		oj := outbounds[j]
+		hi := g.history.LoadURLTestHistory(RealTag(oi))
+		if hi == nil {
+			return false
+		}
+		hj := g.history.LoadURLTestHistory(RealTag(oj))
+		if hj == nil {
+			return false
+		}
+		return hi.Delay < hj.Delay
+	})
+	return outbounds
+}
+
+func (g *URLTestGroup) loopCheck() {
+	go g.checkOutbounds()
+	for {
+		select {
+		case <-g.close:
+			return
+		case <-g.ticker.C:
+			g.checkOutbounds()
+		}
+	}
+}
+
+func (g *URLTestGroup) checkOutbounds() {
+	b, _ := batch.New(context.Background(), batch.WithConcurrencyNum[any](10))
+	checked := make(map[string]bool)
+	for _, detour := range g.outbounds {
+		tag := detour.Tag()
+		realTag := RealTag(detour)
+		if checked[realTag] {
+			continue
+		}
+		history := g.history.LoadURLTestHistory(realTag)
+		if history != nil && time.Now().Sub(history.Time) < g.interval {
+			continue
+		}
+		checked[realTag] = true
+		p, loaded := g.router.Outbound(realTag)
+		if !loaded {
+			continue
+		}
+		b.Go(realTag, func() (any, error) {
+			ctx, cancel := context.WithTimeout(context.Background(), C.TCPTimeout)
+			defer cancel()
+			t, err := urltest.URLTest(ctx, g.link, p)
+			if err != nil {
+				g.logger.Debug("outbound ", tag, " unavailable: ", err)
+				g.history.DeleteURLTestHistory(realTag)
+			} else {
+				g.logger.Debug("outbound ", tag, " available: ", t, "ms")
+				g.history.StoreURLTestHistory(realTag, &urltest.History{
+					Time:  time.Now(),
+					Delay: t,
+				})
+			}
+			return nil, nil
+		})
+	}
+	b.Wait()
+}